Elutriator for hydrocarbon conversion systems



R. KOLLGAARD 2,656,920

ELUTRIATOR FOR HYDROCARBON CONVERSION SYSTEMS 3 Sheets-Sheet 1 Oct. 27,1953 Filed April 50, 1952 INVENTOR REYNER KULLEAARD ATTORNEY Oct. 27,1953 R. KOLLGAARD 2,656,920

I ELUTRIATOR FOR HYDROCARBON CONVERSION SYSTEMS Filed April 30, 1952 3Sheets-Sheet 2 INVENTOR REYNER KULLBAARD Oct. 27, 1953 R. KOLLGAARDELUTRIATOR FOR HYDROCARBON CONVERSION SYSTEMS Filed April 50, 1952'xxmu-mamumwmm .315

3 Sheets-Sheet 3 INVENTO'R REYNER KULLBAARD ATTORNEY Patented Oct. 27,1953 ELUTRIATOR FOR HYDROCARBON CONVERSION SYSTEMS Reyncr Kollgaard,Media, Pa., assigno'r to Houdry Process Corporation, Wilmington, Del., acorporation of Delaware Application April 30, 1952, Serial No. 285,269

12 Claims. I

This invention relates to a method and apparatus for elutriatinggranular contact material for the removal of small-size particles,particularly as applied to the circulatory system of a catalytichydrocarbon conversion unit.

The invention is particularly adapted for use in a hydrocarbonconversion system involving the continuous circulation of granularcontact material having a particle-size in the order of about 1-15, andpreferably 2-8, millimeters in diameter, which circulatory systemincludes a down-flow path through which the contact material gravitatesas a compact moving mass, and an up-fio'w path through which the contactmaterial is pneumatically elevated for return to the upper end of thedown-flow path.

A typical system to which the present invention may be applied isdisclosed in an article entitled Houdrifiow: New Design in CatalyticCracking, appearing at page 78 of the January 13, 1949, issue of the Oiland Gas Journal. The pneumatic lift disclosed in the article comprisesan elongated vertical lift pipe having its lower inlet end. portionextending into a lower li ft hopper or engager, wherein contact materialwithdrawn from the lowermost contact zone of the down-flow path isengaged by one or more streams of lift gas and conveyed into and thenupwardly through the lift pipe to an upper lift hopper or disengagercontaining the upper end portion of the lift pipe. Within the disengagervessel, the contact 'material discharged from the upper endof the liftpipe is separated from the accompanyinglift gas by gravitationaldeceleration and free fall of the particles of contact material. Thedisengaged contact material gravitates to the lower region of the liftdisengager, from which regionitis continuously withdrawn and returned tothe upper end of the down-flow path. The lift g'as, substantially freeof contact material, is separately removed and is passed to conventionalmeans, such as a cyclone separator, for the usual removal of entrainedfines, i

It is a common practice in such systems to continuously by-pass aportion or the circulating contact material to an elutriator iorthe'purpose oi removing fines from the system, the fines being consideredthose particles which are about 14 mesh or smaller in size. Thelarger-size particles, which are suitable for reuse, are then returnedto the circulatory system at any oneof several points in the circulatorypath suitable for thereintr'oduction of'the contactniaterial.

Heretofore, it has been apractice to withdraw the elutriator feed streamfrom the circulatory system at some convenient location along its pathof travel between the disengager and the point of introduction of thecontact material 'into the hydrocarbon conversion unit. After theremoval of undesired small-size particles, the contact material isreturned to the circulatory system at some convenient lower level, suchas directly into the lift engager.

In accordance with the present invention, the stream of contact materialdischarging upwardly into the lift disengager is intercepted during itsfree fall by tray-like members deposited at a plurality of levelswithinthe disengager vessel. The contact material collected on the traysis passed stagewise downwardly from tray to tray in a plurality ofseparate circumferentiallyspaced streams adjacent to the inner wall ofthe ndisengager, each having a relatively short distance of free fall.From the lowermost tray, the contact material gravitates freely to thelower region of the disengager vessel, from which region it iscontinuously withdrawn and passed downwardly to the uppermost zone alongthe down-flow path of the hydrocarbon conversion unit A portion of thedisengaged contact material is withdrawn from a location on one or moreof the trays of the disengager at which there is a relatively highconcentration of the smaller-size particles of disengaged contactmaterial and is passed by gravity flow to an elutriator for the removalof undesirable small-size particles.

In a preferred embodiment of the invention the elutriator is so locatedthat the separated large-size particles may be passed by gravity flow tothe continuous compact moving mass of contact material gravitatingthrough the down-flow path of the conversion unit. A portion of the liftgas separated from the contact material within the disengager is passedinto the elutriator to effect in known manner therein the desiredseparation of fines from the large-size particles of contact material.The remaining portion of the disengager' gas and the gas dischargestream from the elutriator are both passed to a common cyclone separatorwhich removes the fines from the lift gas and the elutriator gas streamsbefore passing the same to the stack. I

In a multiple lift system employing a plurality of separate disengagers,each serving one passed to a second upper kiln, as disclosed in myapplication, Serial No. 285,270, filed April 30, 1952, the elutriatorvessel and the common cyclone serving the elutriator and the disengagersmay conveniently be located one above the other axially over the upperkiln.

For a fuller understanding of the invention reference may be had to thefollowing descripticn and claims taken in connection with theaccompanying drawings forming a part of this ap plication, in which:

Figure 1 is a sectional view, in elevation, showing one embodiment ofthe invention as applied to a multiple lift system;

Figure 2 is a fragmentary sectional view, in elevation, showing theelongated downcomers at one side of the disengager vessel;

Figure 3 is a horizontal section taken along the line 3-3 of Fig. 1;

Figure 4 is a horizontal section taken along the line i 1 of Fig. 1;

Figure 5. is a horizontal section taken along the line 5--5 of Fig. 1;

Figure 6 is a horizontal section taken along the line B-6 of Fig. 1;

Figure '7 is an elevational view of the disengager vessel, with aportion broken away'to show an embodiment of the invention wherein theelutriator is located internally of the disengager vessel;

Figure 8 is a horizontal section taken along the line ii8 of Fig. 7;

Figure 9 is a horizontal section taken along the line 9-9 of Fig. 7; and

Figure 10 is an elevational view showing the elutriator applied to adisengager which does not have a storage or surge capacity in its lowerregion, the elutriator being positioned axially above and in opencommunication with the uppermost zone containing the downwardly movingcompact column of contact material.

Referring to the embodiment of theinvention illustrated in Figs. 1-6,the numeral H refers to thedisengager vessel of a multiple pneumaticlift. The disengager is supported at the upper end of a pair of parallellift pipes l2, and comprises an upper cylindrical portion 13 and a lowerconical portion. l4 eccentrically attached along its base to the lowerperimeter of the cythrough the sloping side of the eccentric conical.

portion Hi and terminate approximately at the level of the juncturebetween portions l3 and It. The height of the conical portion and thedischarge level of the lift pipes are such as to provide sufficientspace in the bottom of the disengager for maintaining a compact movingbed it of disengaged contact material as surge capacity for thecirculatory system. The axes of the lift pipes l2 areparallel to theaxis of cylindrical portion; 13, and are equally spaced therefromonacommondiameter. 7

At the lower end of the disengager, the apex of the conical portion M isconnected to an inclined conduit it through which disengaged contactmaterial from bed #5 may be continuously passed in the form of a compactmoving column to the uppermost contact zone along the down flow path ofthe conversion unit, such as the reactor, not shown. 7

Within the disengager II the streams of contact materialand lift gasdischarging from the streams to tray segment 18 next below.

The trays are located outside the approximate envelope of the risingstreams of contact material, and are arranged to intercept the freelyfalling particles and to pass them stagewise from tray to tray untilthey reach the surface of the bed I5 in the lower region of thedisengager.

The first, or uppermost, pair of tray segments I! and I1, shown in Figs.1, 2 and 3, are located in the upper region of the disengager at a levelwhich is attained, for the most part, only by the smaller-size particlesin the rising streams of contact material. As the completely deceleratedparticles become disengaged from the lift gas and gravitate toward thebottom of the disengager, those particles which are in the pe ripheralregion of the vessel above the first tray segments are depositedthereon, while the centrally located particles pass downward between thefirst tray segments to be deposited at a lower level.

Tray H is provided with an arcuate dam or weir 2| which serves to retainon the surface of the tray a static accumulation of the particlesdeposited thereon. Additional particles slide downwardly over thesurface of the static mass and pass over the dam into the arcuate spacebetween the dam and the wall of the vessel, from which space theparticles drain through openings 22 and fall freely to the peripheralregion of the tray segment [8 next below.

Tray I1 is similar to tray ll, with the exception of the provision fordrain. Instead of drain openings, such as 22, tray I1 is provided with aplurality of parallel downcomers 23, two being illus trated, whichconvey the particles as confined The discharge ends of downcomers 23 arepreferably located a short distance above the receiving tray.

The next lower pair of tray segments l 8 and 18' are of similar shape,as shown in Figs. 1, 2 and 4, but extend inwardly a greater distancetoward the central region of the disengager. ally, however, both traysegments have a plurality of parallel dams 24 forming spaced chords ofthe arcuate dams 2i. Openings 22 in tray l8 permit the contact materialto fall freely to tray i9 next below. Tray I8 is provided with aplurality of downcomers 25, two being shown, whose upper ends aredisposed directly below the discharge ends of downcomers 23, and whichconverge so that their lower ends areat a single receiving [9, shown inFigs. 1, 2 and 5, have irregular inner edges, the edges beingextendedcentrally to meet in a relatively narrow region'at the center ofthe vessel, thus forming openings 26 of 'sufiicient size to permit freepassage of the separate rising streams of contact material.

lift pipes i2 expand and merge in the upper re- 'jgion of thedisengagerf The approximate enalso are provided with arcuate dams 2 I'and with straight parallel dams 24. Openings 22 are provided along theentire peripheral annularspace oftray l9, and at each end portion oftheperipheral annular space of tray I 9'. Trayle' is provided with a singlevertical downcomer ,2!

Addition- 7 Trays l9 andlil' whose? inlet end? is located immediatelyBeneath hie-aforementioned single receivin Trays 211' and showni Figs; Eand 6;- are tireiowermost trays: 'Fh'ey p'rojeot a mamas short distanceinwardly from the vessel wall but extend circumferentialiy along thewall of the vessel a greater distance than any of the traps above. Trays20* and 21'!" receive all tlie contact material failingiree-ly throughthe: openings: 21' of trays l9 and l9.

The slope" and sizeof all the-trays and tlietotal flow area of thedrains on" each tray are such as to" preclude; or at least minimize, anyspill over of contact rrlaterial from the inner edges of the trays.Where the slope of the trays for" any reason is not suflicient to assurefieedom from spill-over, additional dams may-locprowlded al'ong theinnermost edges'of each tray-1 Byrea'son of the fact that t'l'ie smallerparticles tendto'require-a greater disengaging heigliiithan the largerparticles, theccmcentra-tiion of smalls'ize particles increases or; inother words; the average particle size' decreases upwardly through thenew system: I v

Dow'nco'mers 23 therefore convey streams of contact material whichhavethe highest'concentration of small-size particles: Since the in-l'etends" of" downcomers 25 are adjacent to and directly below' the"discharge endsof down'comers 23, theformer will preferentially withdrawfrom the material on tray is" that which has eeenreceived from tray I1".Similarly; downcom'erfl preferentially withdraws from trayl9" thatmaterial which has been deposited thereon from downcomer's' 25'.

Downco'mer 21 is closed at its lower end, but has a side outlet adjacenttheretoi From the lower end of the downcomer the contact material isassed into" a conduit 2'8- through whichthe material is conveyed bygravity flow outwardly throughthe wall of the' disengagertoanelutriator, generall'yindicated by the numeral 29 Gonduit 28 has ashort vertical run 30 provided with an orifice plate 3 l" to control theflow of contact material to be elut'riated. w

The elutriator' 29 comprises a hollow cylindrical member 32havingitslower portion depending concentrically within a closedcylindrical chamber 33 of substantially greater diameter. The

lower end of conduit 28' extends into the upper region of cylindricalmember 3? and is arranged to discharge the contact material axiallydownward therein. A distributor plate" 3 4 is supported axially belowthe end of conduit 23 to intercept and distribute outwardly" the fallingstream of particles. 3

Elutriator gas is provided by withdrawing a portion of the disengagedlift gas from the di' engager fl through conduit 35. The inlet end ofconduit 35 is located within the disengager at a point approximatelylevel with the lowermost tray segment 20, and between the tray and therising streams of contact material dischargin from the lift pipes ll}such location being selected because the gas. withdrawal does notinterfere with the rise or fall of the contact material. To prevent theadmission of stray particles of contact material into the conduit 35,the inlet end may be turned downward, as shown. The discharge endoffconduit 35 isconn'ected into the side wall of chamber 33 at a levelsubstantially above the open lower end of cylincirical member 32', sothat the elutriat'or gas will first travel downwardly within the annularpassage formed Between the concentric walls of members 3! and 6'. w andthemupmdltr into andthrmiglnthe lattes; tn the falling; or!comnctmateriali.

The: remaining: portion: (It. the;- liit'. gas is. dice charged. fromdisengager lilz throughi overhead conduit? 29;. which; iSl provided in:known manner 1 with? a suitable: dampen;.. not shown; for the punpose ofobtaining the desiredipropontioni of; gas flbwto:=the:el'ut1'laton29!'..

elutniator separates;- the?- smahi-size particles; from; the:large-size: particles of, contact. material; the. latter gravitating; tothe surface-.- OIL a moving. beds. 35 of: the same maintained at thebottom of chamber 337; the former? lacing,- car.- ried upwardly out ofi.therelutriator through: condull: 3 by entrainment in thecountercurrcntlyflowing gasstream;

The separated: largc sizea particles are continuously withdrawn: tram:the bottom oil bed; 356 through: conduit iiiijlprovidedi with an orificeplate 35, and'returned'; torthe: disengager Ill. Conduit 38 introdiicesithe: elutriator stream: at particles into the conical portion. I14: at alow point within thecompact moving bed Hi.

In order. to constantly maintain. the; compact moving bed; 3:6 at the:bottom at the: elutriator, a bypass conduit withdraws a portion of. thecontact material flowing. in, the upper portion of vertical run so ofconduit 28 at a. point above. the orifice 31 and) passes the same;downwardly to the surface of the'bed 36. The-discharge: end. of. conduitis belowthe-lower. end of cylindricalmemher 32, and determinesthelevel-of bed 35.

To assure that conduit Ad will. by-pass a, mini- I mum of the:small-size particles the. juncture of conduit 40" with. vertical run. itis preferably at the side directly oppositeztothe side at-whichthecontact material enters the vertical runfrom the upper sloping portionof conduit 28; Thusthere is a minimum: withdrawal of particles from thatportion of the stream flowing through conduit 28- which containsthegreatest concentration of fines. It is known that, by reason of. the.classification: of particles which: inherently occurs. during flowalong'an. inclined path, such as the upper sloping portion of conduit28%;, the small-size particles will flow in the vertical run along thewall portionwhichis nearest-the direction of lateral admission.

Disengager gas ontlet-condint 29- andelutriator gas outlet conduit 31'are preferably hotlr connected to a common cyclone separator; not shown,

for the removal of fine particles carried overhead from the disengager Il and rejected fine particles discharged overhead from the elutriator2.9-.

Referring to the modification; of the invention illustrated in Figs. 7',8' and 9,. the disengager vessel H of Fig. I, with slight modificationofthe internal tray structure, is provided, with an internal elutriator,generally indicated by the numeral ment l9 adjacent to the wall of thecylindrical portion [3. The lower end. of cylinder 52 is open, and theupper end closed by a horizontal end plate 53. End plate 53 has acentral opening to receive the lower end of a gas outlet conduit 54.Aportionof the separated lift gas within the disengage:- cnters thelower end of cylinder 52 and is discharged from the upper end throughcondult 54. End plate 53 also has four uniformly distributed openings,as shown in Fig. 8, to receive the lower endsoif two pairs or downcomers5i and $8. The pair-of conduits 55 which have their discharge endslocated nearest the axis of the disengager have their inlet ends set inthe tray segment I1, and. the pair of conduits 56 whose discharge endsare farthest from the axis of the disengager have their inlet ends setin the tray segment l8. The usual distributor plates 51 are placed belowthe discharge ends of the downcomers, as shown.

All the contact material drained from tray ll is passed through conduits55 to the elutriator, and all the contact material drained from tray [8'is conveyed to the elutriator through downcomers 56. If desired,however, one or more openings 22 may additionally be provided in traysegment IS in either of the embodiments of Figs. 1 and '7.

From the downcomers 55 and 56 the contact material gravitates freelythrough cylinder 52, countercurrently to the stream of lift gas movingtoward the discharge conduit 54. The small-size particles of contactmaterial are carried out of the vessel by entrainment in the discharginggas stream, and the large size particles descend by free fall to thesurface of tray segment 55; Tray segment 58, shown in Fig. 9, issubstituted for tray segment 20' of Fig. 1, and extends inwardly towardthe axis of the disengager sufficiently to intercept all the contactmaterial discharging from the lower end of cylinder 52. Tray 58 also isprovided with openings 22 through which the contact material drains tothe surface of the bed maintained in the'lower end of the disengager. Adrain conduit 59, controlled by valve 53 is provided at the lower levelof tray 58 in order that samples may be withdrawn, as desired.

In the present modification, the gas flowing through the elutriator iscontrolled in the same manner as it is controlled in the embodimentFig. 1. Gas discharge conduits 29 and 54 are connected to a commoncyclone separator, not shown,

for the removal of fines and other rejected par a ticles.

Fig. shows the application of the invention to a system in which surgecapacity, in the form of a compact moving bed, is not provided withinthe disengager vessel, and the contact, material slides freely through adisengager draw-01f conduit to a compact moving bed located at a lowerlevel along the down-flow path. Examples of such arrangement may befound in systems employing a separate surge hopper at the upper end r ofthe conversion unit, and in a split kiln arrangement wherein the reactoris placed between upper and lower kilns, as shown in my companionapplication, Serial No. 285,270 filed April 30, 1952.

In Fig. 10, the elutriator 6! is located externally of the disengager52, A tray structure, diagrammatically shown in broken lines, isprovided within the d sengager 62, and the elutriator feed stream ofcontact material is withdrawn from a tray having a high concentration ofsmall-size particles, such as the upper or the middle trays. l"helutriator feed stream is conveyed through conduit 53, provided with anorifice 64, into the elutriator 6 l.

The elutriator is located axially above a vessel 65 which may be areactor storage hopper or may be the upper kiln of a split-kiln systemsuch as that disclosed in my aforementioned companion case. Axiallyabove the elutriator is a cyclone separator 66 which receives the liftgas discharge from the disengager through conduit 61, as well as thelutriator gas discharge through conduit.

- The gas feed to. the elutriator Bl through con 5 duit 69 may besupplied from any suitable source,

8 such as the lift engager or the kiln. With a split.- kiln system, asabove-defined, the elutriatorgas stream may be conveniently supplieddirectly from the upper kiln, a portion of such gas being by-passed tothe elutriator for this purpose.

With the axial alignment of equipment, as shown, the elutriatorconveniently discharges the returnable contact material verticallydownward into the down-flow path of the circulatory system.

Obviously many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof, and therefore only such limitations should be imposed asare indicated in the appended claims.

What is claimed is:

I 1. In a circulatory system for conveying granular contact materialwherein said material flows compactly downward through at least onecontact zone and is thereafter pneumatically elevated through one ormore lift paths for recirculation, with consequent production of finesby attrition of said granular material, the method which comprisedischarging said pneumatically elevated granular material upwardlywithin an elongated disengaging zone, said zone being of sufficientheight 'to effect the disengagement of said granular material from thelift gas by gravitational deceleration and free fall of the gran ularmaterial, intercepting the freely falling material at one or more levelswithin said disengaging zone located laterally of the discharged streamof granular material and lift gas, passing a portion of said interceptedgranular material by free fall stagewis through said levels to the lowerregion or" said disengaging zone, passing the remaining portion of saidintercepted granular material along at least one confined pathdownwardly from at least one of said levels to an elutriating zone, saidremaining portion having a relatively high concentration of said fines,separating the fines from the large-size particles of granular materialwithin said elutriating zone' by countercurrent engagement with a streamof gas, removing said fines from said circulatory system, and returningsaid large-size particles to said granular material flowing compactlydownward.

2, The method as defined in claim 1 characterized in that said gasintroduced into said elutriatmg zone comprises gas disengaged from saidgranular material within said disengaging zone, and said large-sizeparticles of granular material discharged from said elutriating zone arereturned to said compactly flowing material within the lower region ofsaid disengaging zone.

3. The method as defined in claim 2 further characterized in that saidsmall-size particles are removed from said elutriating zone by saidstream .of gas, and in that the remaining portion of the disengaged liftgas and said streamof gas from said elutriating zone are conveyed to acommon separator for removing all the small-size particles of granularmaterial from said gas.

4. A method as defined in claim 1' in which said disengaged granularmaterial is intercepted within said disengaging zone at a plurality ofvertically-spaced levels arranged to intercept material of differentaverage particle size, decreasing progressively upward, and in which aportion'of the granular material intercepted at one or more uppermostlevels is conveyed stagewise along separate confined paths from level tolevel and subsequently withdrawn as a confined stream'from saiddisengaging zone at a lower 9 level, said separate confined paths beingarranged so that the discharge of granular material from the confinedpaths at one level is directly above the inlet to the confined paths atthe next lower level.

5. A method as defined in claim 1 in which said elutriating zonecomprises a confined zone within said disengaging zone and in opencommunication therewith only at the lower end of said elutriating zone,and wherein granular material is intercepted at one or more levels abovesaid elutriating zone, said intercepted material being conveyed fromeach of said one or more levels along separate confined paths anddischarged directly into the upper region of said elutriating zone, thedisengaged gas being passed, in part, from the lower region of saiddisengaging zone upwardly into the open lower end of said elutriatingzone and, in part, being discharged from th upper region of saiddisengaging zone, the gas and entrained solids being discharged from theupper end of said elutriating zone and passed with said lift gasdischarged from the upper region of said disengaging zone to a commonseparator for removal from the combined gas stream of substantially allthe small-size particles of granular material.

6. In a circulatory system for conveying granular contact materialwherein said material fiows compactly downward through at least onecontact zone and is thereafter pneumatically elevated through one ormore lift paths for recirculation, with consequent production of finesby attrition of said granular material, the method which comprisesdischarging said pneumatically elevated granular material upwardlywithin an elongated disengaging zone, said zone being of sufiicientheight to effect the disengagement of said granular material from thelift gas by gravitational deceleration and free fall of the granularmaterial, intercepting the freely falling material at one or more levelswithin said disengaging zone located laterally of the discharged streamof granular material and lift gas, at least one of said levels beinglocated in a region of said disengaging zone wherein the disengagedmaterial predominantly comprises said fines, passing a portion of saidintercepted material by free fall stagewise through said levels to thelower region of said disengaging zone and thence to the surface of saidcompactly flowing material, passing the remaining portion of saidintercepted material, predominantly comprising fines, to an elutriatingzone, separating the fines from the large-size particles of granularmaterial within said elutriating zone, and retaining said largesizeparticles to said compactly flowing granular material.

'7. In a circulatory system for granular material wherein said materialgravitates as a compact moving column along a down-flow path and isthereafter elevated by means of lift gas through one or more lift pipes,with consequent attrition of said granular material such as to requireremoval from said system of small-size attrited particles, thecombination of a disengaging chamber containing the upper end portion ofat least one of said lift pipes, said disengaging chamber extendingabove the discharge end of said lift pipe 9, distance sufiicient topermit substantially complete gravitational deceleration of granularmaterial discharged from said lift pipe, and having an upper outlet fordisengazed lift gas and a lower outlet for disengaged 10 granularmaterial, one or more trays attached to the side of said disengagingchamber above said discharge end of said lift pipe and adapted tointercept freely falling granular material, at least one of said traysbeing located in the upper region of disengagement to thereby intercepta portion of the disengaged granular material having a relatively highconcentration of small-size particles, an elutriating chamber havingcontact material and elutriating gas inlets, and having an outlet forlarge-size particles of granular material and an outlet for saidelutriating gas and entrained small-size particles of granular material,and means for passing said portion of intercepted granular materialhaving a relatively high concentration of small-size particles to saidelutriating chamber.

8. Apparatus as defined in claim 7 including a cyclone separator, andmeans for conveying thereto both the disengaged lift gas from saiddisengaging zone and the mixture of elutriating gas and entrainedsmall-size particles from said elutriating zone.

9. Apparatus as defined in claim '7 in which said trays are four innumber and are attached to the sides of said disengaging chamber atlongitudinally spaced levels above said discharge end of said lift pipe,and including downcomers in at least the two uppermost trays forconveying the concentrate of small-size particles from said uppermosttrays to said elutriating chamber.

10. Apparatus as defined in claim 9 in which the third tray from the topextends transversely across the disengaging zone and has one or moreopenings adapted to freely pass the streams of contact materialdischarging upwardly from said one or more lift pipes, said third trayhaving set therein a withdrawal conduit which, together with saiddowncomers comprises said means for passing said small-size particles tosaid elutriating chamber.

11. Apparatus as defined in claim 10 in which each of said trayscomprises a pair of diametrically opposite inclined segments whose inneredges are just outside the stream profile of said discharging stream ofgranular material, and in which the segments of said third tray arejoined along a portion of their inner edges.

12. Apparatus as defined in claim 7 in which said trays are four innumber and are attached to the sides of said disengaging chamber atlongitudinally spaced levels above said discharge end of said lift pipe,and in which said elutriating chamber comprises a hollow cylindricalvessel set in the third tray from the top, said elutriator being closedat its top and open at its bottom, and including at least one downcomerset in each of the first and second trays and extending downwardly intosaid elutriator.

REYNER KOLLGAARD.

Germany Oct. 6, 1914 Great Britain May 16, 1929 Number Number

